1. Field of the Invention
The present invention is directed to a torque converter and in particular a torque converter comprising a converter housing, a turbine wheel having a turbine wheel hub and shell arranged in the converter housing and preferably comprising a lockup clutch. A torsional vibration damper arrangement is provided between the converter housing and the turbine wheel hub, wherein the torsional vibration damper arrangement comprises a first transmission arrangement, and a second transmission arrangement which is rotatable about an axis of rotation with the first transmission arrangement.
2. Description of the Related Art
It is known to provide a torque converter comprising a converter housing connectable with a drive shaft, a turbine wheel having a turbine wheel shell and a turbine wheel hub arranged in the converter housing so as to be rotatable about an axis of rotation and which is connectable with a converter driven shaft. It is further known to provide a lockup clutch for optional coupling of the turbine wheel with the converter housing such that it is rotation is substantially fixed with respect to each other. Moreover it is known to provide a torsional vibration damper arrangement in a force flow path between the converter housing and the turbine wheel hub, wherein the torsional vibration damper arrangement comprises the following: a first transmission arrangement, a second transmission arrangement which is rotatable about the axis of rotation with the first transmission arrangement and with respect to the first transmission arrangement, a coupling arrangement which has a torque-transmitting connection with the first transmission arrangement by a first coupling area of the coupling arrangement and which has a torque-transmitting connection with the second transmission arrangement by a second coupling area of the coupling arrangement.
In torque converters of the type mentioned above which have a torsional vibration damper arrangement, this torsional vibration damper arrangement is generally constructed so that it has a primary side receiving introduced torque in pull operation and a secondary side which is coupled with the primary side by a plurality of damping springs arranged about the axis of rotation in the circumferential direction. One side of the primary side and secondary side generally forms a hub disk with respective spring windows and control edges for the springs and the other side comprises respective cover disk elements which lie on both sides of the hub disk and have corresponding spring windows and control edges. When torque is introduced, the damping springs are supported at control edges of the hub disk and of the cover disk elements, so that the primary side and the secondary side are rotatable with respect to one another when the damping springs are compressed in the circumferential direction. In this way, rotational vibrations occurring in a drive system are damped in the region of the torque converter.
Torque converters which are constructed in the manner described above have the disadvantage that they have a fixed damping characteristic defined by the spring characteristic of the damping springs. Therefore it is generally extremely difficult, if not impossible, to adapt to different operating states of the drive system in which different rotational vibrations with different frequencies are to be expected. Another problem is that the damping springs can change over the relatively long life of such drive systems because of permanent stressing or loading of the damping springs due to fatigue of their spring characteristic. This can lead to an unwanted change in the damping characteristic of the entire torsional vibration damper arrangement.